[PATCH v5 0/9] blk-mq: Implement runtime power management

Bart Van Assche
2018-08-07T22:51:24Z

Hello Jens,

This patch series not only implements runtime power management for blk-mq but
also fixes a starvation issue in the power management code for the legacy
block layer. Please consider this patch series for kernel v4.19.

Thanks,

Bart.

Changes compared to v4:
- Dropped the patches "Give RQF_PREEMPT back its original meaning" and
"Serialize queue freezing and blk_pre_runtime_suspend()".
- Replaced "percpu_ref_read()" with "percpu_is_in_use()".
- Inserted pm_request_resume() calls in the block layer request allocation
code such that the context that submits a request no longer has to call
pm_runtime_get().

Changes compared to v3:
- Avoid adverse interactions between system-wide suspend/resume and runtime
power management by changing the PREEMPT_ONLY flag into a counter.
- Give RQF_PREEMPT back its original meaning, namely that it is only set for
ide_preempt requests.
- Remove the flag BLK_MQ_REQ_PREEMPT.
- Removed the pm_request_resume() call.

Changes compared to v2:
- Fixed the build for CONFIG_BLOCK=n.
- Added a patch that introduces percpu_ref_read() in the percpu-counter code.
- Added a patch that makes it easier to detect missing pm_runtime_get*() calls.
- Addressed Jianchao's feedback including the comment about runtime overhead
of switching a per-cpu counter to atomic mode.

Changes compared to v1:
- Moved the runtime power management code into a separate file.
- Addressed Ming's feedback.

Bart Van Assche (9):
block: Change the preempt-only flag into a counter
block: Move power management code into a new source file
block, scsi: Introduce blk_pm_runtime_exit()
percpu-refcount: Introduce percpu_ref_is_in_use()
block: Change the runtime power management approach (1/2)
block: Change the runtime power management approach (2/2)
block: Remove blk_pm_requeue_request()
blk-mq: Insert a blk_pm_put_request() call
blk-mq: Enable support for runtime power management

block/Kconfig | 5 +
block/Makefile | 1 +
block/blk-core.c | 277 ++++----------------------------
block/blk-mq-debugfs.c | 11 +-
block/blk-mq.c | 8 +
block/blk-pm.c | 230 ++++++++++++++++++++++++++
block/blk-pm.h | 33 ++++
block/elevator.c | 26 +--
drivers/scsi/scsi_lib.c | 17 +-
drivers/scsi/scsi_pm.c | 1 +
drivers/scsi/sd.c | 10 +-
drivers/scsi/sr.c | 4 +-
include/linux/blk-mq.h | 2 +
include/linux/blk-pm.h | 26 +++
include/linux/blkdev.h | 38 ++---
include/linux/percpu-refcount.h | 2 +
lib/percpu-refcount.c | 40 +++++
17 files changed, 420 insertions(+), 311 deletions(-)
create mode 100644 block/blk-pm.c
create mode 100644 block/blk-pm.h
create mode 100644 include/linux/blk-pm.h

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2.18.0